bug(sim/flow): Record capacity changes on idle outlets

This change fixes an issue with the `ForwardingFlowMultiplexer` where
the capacity of new outlets were not recorded correctly due to no
handler being attached to idle outlets, causing the `pull` events to be
disregarded.

This bug manifested in an issue where the CPU counters where reporting
negative values. This was caused by the CPU usage/demand being
subtracted from a zero capacity.

1 files changed, 10 insertions, 3 deletions

diff --git a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/mux/ForwardingFlowMultiplexer.java b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/mux/ForwardingFlowMultiplexer.java
index abe3510b..e0564cd2 100644
--- a/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/mux/ForwardingFlowMultiplexer.java
+++ b/opendc-simulator/opendc-simulator-flow/src/main/java/org/opendc/simulator/flow2/mux/ForwardingFlowMultiplexer.java
@@ -182,6 +182,9 @@ public final class ForwardingFlowMultiplexer implements FlowMultiplexer, FlowSta
 
         activeOutputs.set(slot);
         availableOutputs.set(slot);
+
+        port.setHandler(IDLE_OUT_HANDLER);
+
         return port;
     }
 
@@ -270,11 +273,15 @@ public final class ForwardingFlowMultiplexer implements FlowMultiplexer, FlowSta
         public void onUpstreamFinish(InPort port, Throwable cause) {}
     }
 
-    private static class IdleOutHandler implements OutHandler {
+    private class IdleOutHandler implements OutHandler {
         @Override
-        public void onPull(OutPort port, float capacity) {}
+        public void onPull(OutPort port, float capacity) {
+            ForwardingFlowMultiplexer.this.capacity += -port.getCapacity() + capacity;
+        }
 
         @Override
-        public void onDownstreamFinish(OutPort port, Throwable cause) {}
+        public void onDownstreamFinish(OutPort port, Throwable cause) {
+            ForwardingFlowMultiplexer.this.capacity -= port.getCapacity();
+        }
     }
 }